Preheat the oven to 350° and grease a loaf pan, or use parchment paper.
Beat the sugar and butter together until nice and fluffy. Add in the eggs one at a time and mix well. Pour in the buttermilk, lemon zest and vanilla and mix well.
In a medium bowl, whisk the flour, baking soda and salt together. Add this to the wet ingredients and mix until just combined.
Pour half of the batter into the loaf pan and spread out evenly. Take the fruit preserve and spread it evenly on top of the lemon batter. Pour the rest of the lemon batter on top and spread evenly. Do this carefull to not over mix the preserve into the batter.
Bake in the oven for 50 minutes or until a toothpick comes out clean.
While the lemon blueberry loaf bakes, make the glaze. Whisk together the icing sugar and the lemon juice and until nice and smooth.
After the loaf is done, let it cool in the pan for 10 minutes. Transfer to a wire rack and let it cool before glazing!